Twitter's User Problem: Fastest Gains Are People That Don't See Ads

Nearly 40 Million Active Users Don't Use Twitter's Site or App

Investors who drove up Twitter Inc.'s market value by more than $3 billion this week might want to read the fine print.

The company on Tuesday reported that its second-quarter revenue more than doubled, and growth in the number of people using its service is rebounding, a positive sign for investors who feared Twitter's popularity had peaked.